A portion of the collection showing the Meadowlands' bee diversity. Some species came from Africa and Europe.

The bee survey is part of a larger effort by the Meadowlands Commission to document animal and plant species and better understand how changes to the environment are affecting the region's biodiversity.

"I was amazed by the amount of bee species found. I was thinking 12, maybe 13 species," said Francisco J. Artigas, executive director of the Meadowlands Environmental Research Institute.

Prompted in 2007 by the collapse of honeybee colonies, the institute decided to provide grants for insect studies. Bees play a vital role for humans because they pollinate plants.

"The question was, are we providing enough functional habitat to native bees that could help take over the role of the honeybee? At the end of the day we're going to have to fall back for help on our native pollinators," Artigas said.

To trap bees for the count, small plastic bowls of soapy water were set out in four different locations for 24-hour periods. The soap reduced the water's surface tension, so the bees couldn't bounce off. Once in the water, they drowned.

The bowls were painted fluorescent blue, yellow or white — hues that attract bees. "Bees can see more of the color spectrum than we can, and the colors serve as nectar guides. Flowers that might simply look white to us have patterns in them which act like neon arrows for the bees, saying 'Check it out!' " said Sarah Kornbluth, a third-year doctoral student in biology at Rutgers University, who carried out the study along with Gareth Russell, a biology professor at the New Jersey Institute of Technology.

Once collected, the bees were washed in alcohol, dried, sorted by appearance and mounted with pins in shallow boxes.

Identifying a species is tedious because there are more than 20,000 species of bees. There are more than 400 species of bees in the New York area alone.

Researchers begin by looking at basics — is the bee green or black? How long is it? Does it have one mid-tibial spur or two? A microscope helps detect tiny differences, such as the curve of a wing vein, or the extent of pitting on the exoskeleton, Russell said.

Bees can be brown, green, even metallic blue. Many are far smaller than the bumblebee.

Two of the specimens completely befuddled Kornbluth and Russell, so they turned for help to the American Museum of Natural History, which has a global bee collection of 7,000 species. With aid from experts in Europe, they were able to tentatively identify one species as a European thistle bee, black with yellow and orange markings. The other they believe is a North African bee with a yellow face and red tail, and is very obscure, even in its native land. Neither had been recorded in North America before.

Non-native species are showing up more frequently in the New York area because of the growth in global trade, said John S. Ascher, the bee database project manager at the Natural History museum.

The bees can nest or hibernate in a cavity in the wood of shipping crates or pallets. That's how the giant Asian resin bee arrived in New Jersey. The wool carder bee, native to Europe, flourished in the Bronx and Harlem, and spread across the continent.

"Relatively few people are looking for bees, but those who are are finding more odd species," Ascher said.

In the past, bugs may never have survived the long trip across oceans, but today, ships are much faster. "We expect to see these hitchhikers now," Ascher said.

Some newcomers prove useful — the alfalfa leaf cutter bee has been a great pollinator for alfalfa growers. But others are parasitic or bring new diseases with them, posing a threat to native species.

Erik Kiviat, executive director of Hudsonia Limited, a non-profit research institute in Annandale, N.Y., has studied biological diversity in the Meadowlands for more than a decade, and is co-writing a book on the subject. "These urban industrial wastelands that are so common in our area really do support a wide variety of animals and plants, and we're just starting to learn how they can be fostered, protected and preserved," he said.

Kiviat studied dragonflies and frogs in the Meadowlands in 2006. "It's a lousy place for frogs," he said. Frogs generally need fresh or almost-fresh water, while the Meadowlands has become more brackish with salt water intrusion.

"To understand the biological diversity in urban areas you can't just study birds and fish. You need to look at a wide range of species, because birds and fish don't necessarily predict what's happening to other species," Kiviat said.

Given the honeybee collapse, researchers suspect some of the native species may also have declined, Kornbluth said. But nobody knows for sure.